224) Royal Irish Academy. 



having formed on the top of a large cross of common crystals, 

 they must have been generated under circumstances either on a 

 lower temperature or a less concentrated solution than that 

 by which the common variety is produced. If the new- 

 formed crystals be dissolved in water, it is under the ordinary 

 form that they recrystallize. 



When iodide of potassium is crystallized in leaden or tinned 

 iron vessels, Mr. Scanlan has informed me that the crystalline 

 form is altered, from the presence of a minute quantity of 

 iodide of tin or lead ; but what the alteration is exactly, I do 

 not believe has been determined. Having heard the fact, 

 however, from my friend Mr. Scanlan, I sought for metallic 

 impurity in the crystals now described, but in vain. They are 

 chemically pure. 



XLII. Proceedings of Learned Societies. 



ROYAL IRISH ACADEMY. 



Nov. 11, "D EV. Dr. Dickinson gave a verbal account of a remark- 



1839. -*-«- able waterspout, which he had observed at Killiney 

 during the last summer. 



Towards the end of the month of July, about 10 a. m,, while 

 standing on the shore of the bay of Killiney, his attention was di- 

 rected by a friend to a waterspout, distant about a quarter of a mile 

 from the land. It was not similar in form to the representations of 

 waterspouts usually given, and may therefore deserve to be noticed. 

 It was shaped like a double siphon, the whole being suspended at 

 a considerable elevation in the air ; the longer end of the siphon 

 reached towards the sea, and appeared to approach it nearer and 

 nearer, till, at length, its waters were distinctly seen rushing into 

 the deep. The loop gradually lowered, as if sinking and lengthen- 

 ing by its own weight, while the upper part of the siphon seemed 

 not to lose in elevation. At length the loop burst, and there were 

 three streams of water pouring into the sea, two of those streams 

 still continuing united by the arch at the top. The breadth of these 

 streams gradually diminished till they became invisible, but their 

 length seemed undiminished as long as they were at all seen. The 

 quantity of water poured down must have been very considerable, 

 as the bubbling of the sea beneath could be distinctly observed. 



Dr. Dickinson was informed that a waterspout fell a few days 

 after inland, towards the Tliree-Rock mountain. It is said to have 

 done some injury ; but his informant did not see it, and he could 

 not, therefore, ascertain its shape. 



November 30, 1839. Mr. Clarke read a paper " On Atmospheric 

 Electricity." 



The author commenced his paper with a description of the appa- 

 ratus which he had emploj'^ed in the experimental investigation of 

 this subject. He showed the inapplicability of the electrometers 



